JPH03156884A - High frequency heating device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a high-frequency heating device for achieving automated defrosting of food products.

2. Description of the Related Art Conventionally, as an example of automating the thawing state of this type of high-frequency heating device (hereinafter referred to as a microwave oven), as shown in FIG. 6, the weight of food on a turntable 12 is detected. A heating sequence corresponding to the weight was controlled by a microcomputer as a control means, and the output of the high frequency radiation means was controlled. That is, when the weight of a certain food is detected by the weight sensor 22, as shown in FIG. 7, the corresponding weight is heated with maximum power for an initially determined time, and thereafter the driving means is repeatedly turned on and off. Control was performed to reduce the output of the high-frequency radiation means per unit time. Note that 5 is a cooling fan that cools the high frequency radiation means 3.

In addition, as seen in Japanese Patent Application Laid-open No. 59-207595, the thawing state of food can be determined based on the temperature dependence of dielectric loss of food.
In some cases, the control means is configured to indirectly grasp the relationship between the detection output in the oscillation frequency band of the high-frequency radiation means and control the output of the high-frequency radiation means based on signal changes detected by an antenna installed in the heating chamber. .

Thawing of food was achieved through such control.

Problems to be Solved by the Invention However, in the above configuration, when the starting temperature of the food is a certain predetermined temperature (for example, the freezer temperature -
18°C) and the shape is standard (for example, square).Depending on the thawing start temperature and shape of the food, the food may be boiled or unthawed, resulting in poor thawing results. It was enough. In addition, a weight sensor for measuring the weight of food requires a turntable, and its configuration is complicated because it detects changes in the capacitance of the sensor due to the weight of the food and detects distortion signals.

In addition, when detecting thawing using the detection means, if the food is lightweight (for example, 100 grams), the output of the high-frequency radiation means may be switched at the point where the signal change of the detection means increases from the minimum point. Depending on the food (fish), boiling may occur.

Therefore, an object of the present invention is to realize defrosting of food with a simple configuration.

Means for Solving the Problems In order to solve the above problems, the present invention provides that when the signal of the detection means detects a certain threshold value within a predetermined time from the start of decompression, the signal of the detection means and is constituted by a control means for controlling the power of the high frequency radiation means to be reduced or gradually reduced regardless of the relation.

According to the present invention, when a signal radio wave from the high frequency radiating means is applied to a frozen food, if the food is below the freezing point due to an increase in dielectric loss due to heating of the frozen food, the high frequency is difficult to be absorbed by the food. When the weight of the frozen food is small, the absolute amount absorbed by the food is also small, so the detection output has the effect of increasing.

EXAMPLE Hereinafter, an example of the present invention will be described based on the accompanying drawings.

FIG. 1 is a block diagram of the main body of a high-frequency heating device according to an embodiment of the present invention.

1 is food, 2 is a heating chamber, 3 is a high frequency radiation means (hereinafter referred to as magnetron), 4 is a high voltage transformer for operating magnetron 3, 5 is a cooling fan for cooling magnetron 3, and 6 is an antenna for magnetron 3. 7 is an attenuator, 8 is a detection means, 9 is an amplifier for amplifying the detected signal, and 10 is for the high-frequency power of the magnetron 3. The variable driving means 11 is a control means (a microcomputer in the present invention) that controls the driving means 10 according to the amplified detection signal and adjusts the output of high frequency power.

FIG. 2 is a circuit diagram of the detection means 8 for detecting the oscillation signal of the magnetron 3. 14 is a 50 ohm resistor, 15 is a detection diode (for example, a Schottky barrier diode), 16.17 is a resistor, and 1 is a capacitor, which detects the high frequency power that is not absorbed by the food 1 in the oscillation frequency band of the magnetron 3. Detected as voltage ■S. Note that 7 is an attenuator, and the high frequency power that the magnetron 3 radiates into the heating chamber 2 is several hundred watts, and is used to prevent excessive input from entering the detection means 8.

FIG. 3 is a diagram in which the detection means 8 is composed of a microstrip line.

Copper foil patterns 18 and 19 are etched onto a dielectric substrate 19 having a certain dielectric constant ER. The copper foil section 20 has a characteristic impedance of 50 ohms, and the section 21 is grounded. By configuring the detection means 8 on the microstrip line, it is easy to optimally design the length of the line according to the frequency band to be detected, and since this is done by etching, the detection accuracy is improved. .

FIG. 4 is a characteristic diagram showing the relationship between the signal level of the detected voltage Vs and the minimum point T with respect to the weight of the food. From this figure, it can be seen that there are large differences in the detection voltage immediately after the start of thawing and the detection time of the minimum point T, depending on the weight of the food. This is because when the weight of food is small, less high frequency waves are absorbed and relatively more high frequency waves are detected by the antenna.

Figure 5 shows food 1 (frozen minced meat 10
FIG. 3 is a characteristic diagram showing the change in the signal voltage detected by the detection means 8 and the state of the human power of the magnetron 3 when a sample (0 grams) is thawed. In FIG. 5, when the food temperature reaches around 12° C., the detection voltage S of the detection means 8 suddenly decreases. This is because when a part of the food 1 reaches near the freezing point, dielectric loss increases and high frequencies begin to be absorbed in that part.
This is because the high frequency waves detected by the detection means 8 are relatively reduced. However, if the food 1 is heated at the maximum power until the time Tl when the detected voltage VS is at its minimum value by the detection means 8, boiling will occur. The detected voltage vS is heated for a certain time (Tl')L regardless of the signal, and thereafter the control means 11 controls the drive means 10 on and off at appropriate time intervals to perform defrosting.

Note that an inverter circuit may be used as the drive means 10 to control the output power of the magnetron 3, and the present invention is not limited to this embodiment.

Effects of the Invention As described above, according to the present invention, the following effects can be obtained.

The high frequency in the frequency band of the high frequency radiation means is detected by an antenna placed inside the heating chamber, and the weight of the food is determined by whether the voltage detected by the detection means after thawing has started exceeds a certain threshold level. Since it can be determined, even lightweight foods can be thawed optimally without failure.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main body of a high-frequency heating device according to an embodiment of the present invention, FIG. 2 is a circuit diagram of the detection means, FIG. 3 is a cross-sectional view of the detection means configured on a microstrip line, and FIG.
The figure is a characteristic diagram of the change in the signal of the detection means with respect to the food weight during thawing, Figure 5 is a characteristic diagram showing thawing control with 100 grams of minced food, and Figure 6 is a block diagram of the main body of a conventional high-frequency heating device. FIG. 7 is a sequence control diagram of the decompression. 1... Food, 2... Heating chamber, 3...
... High frequency radiation means, 6 ... Antenna, 8.
...Detection means, 1o...Driving means, 11
...control means.

Claims (1)

[Claims] a heating chamber into which food is taken out and taken out; a high-frequency radiating means for supplying high-frequency power into the heating chamber; a driving means for driving the high-frequency radiating means; and a control means for controlling the driving means;
It consists of an antenna shorter than 1/4 wavelength of the oscillation frequency of the high-frequency radiation means, and a detection means for detecting the progress of defrosting of the food through the antenna, and the control means is configured to detect the progress of defrosting the food within a predetermined time from the start of defrosting. A high-frequency heating device configured to perform control such that when a signal from the detection means detects a certain threshold value, the power of the high-frequency radiation means is reduced or gradually reduced regardless of the signal from the detection means.